JPH0359992B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field] The present invention relates to an alkaline degreasing aqueous solution (applied to remove oil stains, etc. from metal surfaces such as steel sheets, galvanized steel sheets, and alloyed galvanized steel sheets) especially at low temperatures (35 to 45°C). (hereinafter referred to as alkaline degreasing liquid). More specifically, in order to fully realize the purpose of the chemical conversion treatment and painting of the metal surface, the present invention provides a method of cleaning the surface of the metal before the chemical conversion treatment, particularly by spray degreasing or immersion at a low temperature of about 40°C. This invention relates to an alkaline degreasing liquid that maintains low foaming properties and exhibits excellent surface cleaning effects in degreasing. [Prior art] Products made of the metals mentioned above are generally subjected to chemical conversion treatment before painting, and the treatment process is usually surface cleaning (degreasing) → water washing (multi-stage method) → surface conditioning → chemical conversion treatment → water washing. (Multi-stage method) → Washing with deionized water → Draining and drying → Painting (anionic or cationic electrodeposition, electrostatic painting, powder coating, painting by spraying or coating, etc.), and alkaline degreasing for surface cleaning. Liquids have been introduced in numerous documents so far. Alkaline degreasing agents usually consist of an alkali builder (an alkaline compound that is the main component of alkaline degreasing agents), a surfactant, and an antifoaming agent. Used as a degreasing liquid). This alkaline degreasing liquid is applied to remove oil, dirt, etc. from the surface of the metal to be treated by spraying or dipping. It is a quantile. Recently, there has been increasing interest in alkaline degreasing agents and alkaline degreasing liquids that can be used especially at low temperatures for the purpose of energy saving. It had one of the following drawbacks. In other words, a) there is intense foaming during the degreasing process, b) when the degreasing liquid that has low foaming properties (foam-inhibiting properties) but poor degreasing power foams, and b) bubbles overflow outside the degreasing tank.
(2) Causing a large amount of alkaline degreasing liquid to disappear. When degreasing metal products having a bag-like structure or a box-like structure by immersion, bubbles are mixed into the inner surface of the metal product at the beginning of immersion, and the bubbles are removed from the inner surface. This prevents the alkaline degreasing liquid from coming into contact with the inner surface of the metal product. Therefore, internal degreasing becomes incomplete. [Object of the invention] The present invention solves the above-mentioned drawback b of alkaline degreasing liquids used particularly at low temperatures (35 to 45°C), and can be used at low temperatures of 40°C without impairing foam control properties. Another object of the present invention is to provide an alkaline degreasing solution that can exhibit excellent degreasing power. [BRIEF DESCRIPTION OF THE INVENTION] The alkaline degreasing solution of the present invention is applied to surface cleaning as a pretreatment for metal chemical conversion treatment, and the degreasing solution comprises at least an alkali builder, a surfactant, an antifoaming agent, and water. The alkali builder includes at least a surface conditioner containing titanium, sodium nitrite, sodium phosphate, and sodium carbonate, and the surfactant includes an alkyldimethylamine oxide, polyoxyethylene nonyl phenyl ether (HLB11-15) The blending ratio of each component of the alkali builder, the surfactant, and the antifoaming agent is such that when the total of the alkali builder, the surfactant, and the antifoaming agent is 100% by weight, The activator is 1 to 5% by weight of the alkyldimethylamine oxide and 4.6% of polyoxyethylene nonyl phenyl ether.
5.6 to 10.5% by weight including 8.5% by weight, the antifoaming agent accounts for 4.7 to 6.8% by weight, the remainder consists of the alkali builder, and the alkyldimethylamine oxide contains the alkaline degreasing solution 1.
It is characterized by containing 0.1 to 2 g. [Description of the structure of the invention] The essential composition components of the alkaline degreasing liquid of the present invention are:
Alkyldimethylamine oxide, polyoxyethylene nonyl phenyl ether (HLB11~
15), is an alkali builder and antifoaming agent. The alkyldimethylamine oxide is a nonionic surfactant having the structure of the following general formula. Here, R is an alkyl group having at least one carbon number from 12 to 22 and is a hydrophobic group mainly composed of a saturated hydrocarbon group. Therefore, the R
may be one alkyl group, such as a lauryl group (C ₁₂ H ₂₅ ⁻ ) or a stearyl group (C ₁₈ H ₃₇ ⁻ ), or a mixture thereof. Moreover, the R may be synthesized, extracted from a natural product, or derived therefrom,
Even for straight-chain alkyl groups, the branching technique It may also be an alkyl group. Further, R is mainly composed of a saturated hydrocarbon group and usually does not contain an olefinic unsaturated bond, but it may also contain an olefinic unsaturated bond such as an oleyl group. . R is coconut oil, soybean oil, palm oil, sesame oil,
The alkyl group can be obtained by hydrogen reduction of a fatty acid constituting at least one fat or oil among natural vegetable oils such as sunflower oil, safflower oil, and olive oil, and animal fats such as pork and beef tallow.
The R may be derived from one of the above-mentioned natural vegetable oils or animal fats, or may be derived from a mixture of two or more of the above-mentioned natural vegetable oils or animal fats. And the R is
It is mainly a saturated hydrocarbon group, and may contain an unsaturated bond depending on the conditions of hydrogen reduction or other reduction. The content of alkyldimethylamine oxide in the alkaline degreasing solution of the present invention is 0.1 g/ to 2 g/, particularly preferably 0.1 g/ to 1 g/1 of the alkaline degreasing solution. If it is lower than 0.1g/, the degreasing improvement effect of alkyldimethylamine oxide (especially the degreasing improvement effect at low temperature (40℃)) can hardly be expected, but a satisfactory degreasing effect is provided within the range of 0.1 to 1 g/ do. Furthermore, even if the content of the alkyldimethylamine oxide is increased to 2 g/l, the degree of improvement in the effect is low, so as mentioned above, the range of 0.1 to 1 g/l is usually sufficient. Since the effect of improving the degreasing power cannot be obtained even if the concentration exceeds 2 g/2, the concentration of alkyldimethylamine oxide in the alkaline degreasing solution of the present application is set at 2.
g/ is the upper limit. As for the method of adding the alkyl dimethylamine oxide, it may be added separately to the alkaline degreasing agent in the degreasing tank, but if the alkyl dimethyl amine oxide is added in the alkaline degreasing solution from 0.1 to 2.
g/, more preferably 0.1 to 1 g/
In order to be able to maintain the concentration at , it is better to incorporate alkyldimethylamine oxide during the production of the alkaline degreaser to be added to the degreaser. For this purpose, 1 portion of alkyl dimethylamine oxide is added to the alkaline degreaser.
It is preferable to mix it in an amount of about 5% to 5%. The main components other than the alkyldimethylamine oxide that are blended into the alkaline degreasing solution of the present invention include (a) polyoxyethylene nonyl phenyl ether, (b) an alkali builder, and (c) an antifoaming agent. These will be explained below. a Other surfactants The alkaline degreasing solution of the present invention contains an alkyldimethylamine oxide and polyoxyethylene nonyl phenyl ether (HLB 11-15, cloud point 40°C or less). b Alkali Builder The alkali builder used in the present invention includes a surface conditioner containing at least titanium, sodium nitrite, sodium phosphate, and soda carbonate.
Surface conditioning agents containing titanium are, for example, disclosed in Japanese Patent Publication No. 58-
Publication No. 55229, U.S. Patent No. 2874081, No. 2322349
It is an aqueous solution containing titanium ions or colloidal titanium, as disclosed in Japanese Patent No. 2310239. A surface conditioning agent containing titanium is used to activate the surface of a steel sheet before phosphate coating conversion treatment, and the use of this surface conditioning agent promotes the phosphoric acid conversion coating formation reaction and improves the formation of phosphate coating crystals. Miniaturization can be achieved. The addition of this titanium-containing surface conditioner and sodium sulfite is particularly effective in forming a chemical conversion film. c Antifoaming agent The type of antifoaming agent used in the alkaline degreasing solution of the present invention is not particularly limited. [Effects of the Invention] The alkaline degreasing solution of the present invention contains alkyldimethylamine oxide as a component of the surfactant in an amount of 0.1 to 2 g/1 to 1 of the alkaline degreasing solution.
Contains polyoxyethylene nonyl phenyl ether, alkali builder and antifoaming agent. Therefore, when using this alkaline degreasing liquid, the
Even at low temperatures, the degreasing ability can be improved without impairing the low foaming properties. In other words, when using an alkaline degreasing liquid, the surface of the metal to be treated can be cleaned to a satisfactory degree as a pretreatment for chemical conversion treatment at a low temperature of about 40°C in about 1 minute when spraying or about 2 minutes when dipping. Moreover, it is possible to maintain foam suppressing properties. When the alkyl group of the alkyldimethylamine oxide to be blended is an alkyl group obtained by hydrogen reduction of a fatty acid constituting natural vegetable oil or animal fat or oil such as coconut oil, the alkyl group is linear and has various types. Since it is a mixture of substances, the above-mentioned performance is especially excellent and stable. The alkaline degreasing solution of the present invention may also contain nonionic surfactants and anionic surfactants as other surfactants. When this alkaline degreasing liquid is used, the above effects are further exhibited. [Examples and Comparative Examples] The present invention will be specifically explained below with reference to Examples and Comparative Examples. (1) Alkaline degreasing liquid According to the formulation of each alkaline degreasing agent shown in Examples 1 to 6 and Comparative Examples 1 to 4 in Table 1, the alkaline degreasing agent was thoroughly mixed using a kneader after each formulation. It was adjusted. The products used as raw materials in the formulation are as follows. 18 g of each of the above-mentioned alkaline degreasers was taken and dissolved in water to prepare a solution of 1 part. However, since each degreaser contains a small amount of percolene Z, it does not dissolve completely and becomes slightly cloudy.

【table】

【table】

[Table] (2) Test plate and application of rust preventive oil Rust preventive oil is applied to steel sheets, galvanized steel sheets, and alloyed galvanized steel sheets, but those applied to galvanized steel sheets are comparatively degreased. Steel plates were selected as test plates because they are easy to use. Test plate: JIS-G-3141, SPCC Rust preventive oil: Daphne Oil Coat Z-3 (manufactured by Idemitsu Kosan Co., Ltd.) Rust preventive oil application: After cleaning the test plate with Triclean,
The above rust preventive oil was applied to the surface using a roll coater in an amount of 1 to 2 g/m ² . Test plate A: After applying anti-corrosion oil as described above, the plate was left indoors at room temperature for 7 days. Test plate B: 60℃± after applying anti-rust oil as above
Left in a high-temperature, high-humidity container at 1°C and relative humidity (RH) 95±2% for 4 days. (3) Degreasing test Each alkaline degreasing solution was heated and maintained at 40°C ± 1°C, and three test plates were immersed in it for 2 minutes without touching each other, and then sprayed with water for 30 seconds to remove the test plates. After washing away excess alkaline degreasing liquid from the surface of the test plate, place the test plate vertically.
After being left indoors for 60 seconds, the degreasing performance was immediately evaluated based on the water leakage area (%) of the three test plates. Example: 100...Complete water leakage (excellent degreasing property) 50...50% water leakage (poor degreasing property) The procedure for adding rust preventive oil to alkaline degreasing solution is as follows:
After adding the above-mentioned anti-rust oil at a rate of 2g or 3g per 1 alkaline degreasing solution, the homomixer shown in Fig. 1 (TKHOMOMIXER TYPE HU-
M) was used to rotate an alkaline degreasing solution at an appropriate speed for 20 minutes at 10,000 rpm, and then it was applied to a degreasing test. (4) Foaming test As a foaming test method, since the degreasing liquid is pumped and stirred in an actual immersion degreasing line, the following method was used to simulate this by using the testing apparatus shown in Figure 2. It was carried out by That is, 3 tall beakers 11 (inner diameter 130 mm, height
After pouring 2000ml of alkaline degreasing solution 9 into 300mm),
This is maintained at 40°C±1°C in a constant temperature bath 12. Next, insert the turbine shaft 2 of the homomixer 8 vertically into the center of the side wall of the tall beaker so that the lower end of the stator 5 (cylindrical ring surrounding the turbine 4) is located at a height of 60 mm above the bottom of the tall beaker. Then, move the commutation plate (circular 6) that can move up and down along the support rod 3 and adjust it so that its top surface matches the level of the alkaline degreasing solution.Next, heat the alkaline degreasing solution to 40℃±1℃. While maintaining the temperature at After stirring, immediately remove the homomixer from the tall beaker, and measure the height of the foam from the liquid surface in mm after 30 seconds have passed since the homomixer stopped rotating. The low foaming property is evaluated from the value.As an embodiment of the present invention, Table 1 shows examples of formulations of various alkaline degreasers based on the present invention.
Table 2 shows the test results for alkaline degreasing solutions made with these alkaline degreasers. The results of comparing Examples 1 to 6 and Comparative Examples 1 to 4 can be summarized as follows. a Degreasing test results As a result of holding each alkaline degreasing solution in Examples and Comparative Examples at 40°C ± 1°C and soaking test plate A and test plate B in it for 2 minutes, the alkaline degreasing solution showed no resistance. When no rust oil was added and mixed, the Examples showed better results than the Comparative Examples, although the difference was small. Next, apply 2 coats of anti-rust oil.
In the case of adding 1 g/g and 3 g/, the difference is clear in both cases, and the example clearly shows superior results.
In addition, in the examples, the tendency for the degreasing performance to decrease due to the addition of up to 3 g of rust preventive oil was either not observed or only a slight decrease was observed, and the influence of the mixing of the rust preventive oil was small. It shows things.

【table】

[Table] ◎...Excellent ○...Good △...Possible ×...Possible On the other hand, in the case of the comparative example, it is clear that the degreasing performance is lowered due to the addition of anti-corrosion oil, which is clearly seen compared to the example. It confirms that it is inferior.

[Brief explanation of the drawings] Figure 1 shows the homo mixer (TKHOMOMIXER).
TYPE HU-M), and Figure 2 is a front view of the foaming test device.

DESCRIPTION OF SYMBOLS 1... Motor, 2... Turbine shaft, 3... Support rod, 4... Turbine, 5... Stator, 6... Commutation plate, 7... Holder, 8... Homo mixer, 9... Alkaline degreasing liquid, 10... Bubbles, 11... 3L tall beaker, 12... constant temperature bath.

[Brief explanation of drawings]

Next, in the foaming test, the examples were already excellent (marked ◎), and the results were only good (marked ○) when the rust preventive oil of the alkaline degreasing solution was not added and mixed. On the other hand, in the case of the comparative example, large variations from excellent to poor (x mark) were observed, and it was observed that there was a tendency for more foaming to occur when rust preventive oil was not added and mixed with the alkaline degreasing liquid. Furthermore, even when the comparative examples are individually compared with the examples, the examples show superior results.

Claims (1)

[Claims] 1. A low-temperature (35 to 45°C) solution that is applied to surface cleaning as a pretreatment for chemical conversion treatment of metals and consists of at least an alkali builder, a surfactant, an antifoaming agent, and water.
In the alkaline degreasing liquid, the alkaline builder contains at least a surface conditioner containing titanium, sodium sulfite, sodium phosphate, and sodium carbonate, and the surfactant contains alkyldimethylamine oxide and polyoxyethylene represented by the following general formula. Nonyl phenyl ether (HLB11~15)
and the blending ratio of each component of the alkali builder, the surfactant, and the antifoaming agent is 100% by weight when the total of the alkali builder, the surfactant, and the antifoaming agent is 100% by weight. The surfactant is 1 to 5% by weight of the alkyldimethylamine oxide and 4.6 to 4.6% of polyoxyethylene nonyl phenyl ether excluding the alkyldimethylamine oxide.
8.5% by weight, the antifoaming agent is 4.7% to 6.8% by weight, the remainder is the alkali builder, and the alkyldimethylamine oxide is present in the alkaline degreasing solution 1.
An alkaline degreasing liquid characterized by containing 0.1 to 2g. general formula R is an alkyl group consisting of at least one carbon number from 12 to 22 and mainly consisting of a saturated hydrocarbon group. 2 The alkyl group R hydrogenates a fatty acid constituting at least one of natural vegetable oils such as coconut oil, soybean oil, palm oil, sesame oil, sunflower oil, safflower oil, and olive oil, and animal fats such as pork and beef tallow. The alkaline degreasing liquid according to claim 1, which is an alkyl group added, an alkyl group obtained from polymerization of ethylene monomer, or an alkyl group obtained by decomposition of paraffin.